Field of the Invention
The present invention relates to a silicon carbide semiconductor device and a method for manufacturing the silicon carbide semiconductor device, in particular, a silicon carbide semiconductor device provided with a trench and a method for manufacturing such a silicon carbide semiconductor device.
Description of the Background Art
In recent years, in order to achieve high breakdown voltage, low loss, and utilization of semiconductor devices, such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor, under a high temperature environment, silicon carbide has begun to be adopted as a material for a semiconductor device. Silicon carbide is a wide band gap semiconductor having a band gap larger than that of silicon, which has been conventionally widely used as a material for semiconductor devices. Hence, by adopting silicon carbide as a material for a semiconductor device, the semiconductor device can have a high breakdown voltage, reduced on-resistance, and the like. Further, the semiconductor device thus adopting silicon carbide as its material has characteristics less deteriorated even under a high temperature environment than those of a semiconductor device adopting silicon as its material, advantageously.
In a MOSFET including a substrate having a main surface in which a trench is formed, an electric field is concentrated at a corner portion formed by a side portion, which forms the trench, and the main surface of the substrate with the result that a gate insulating film formed in the vicinity of the corner portion may be broken. For example, Japanese Patent Laying-Open No. 2012-74720 describes a silicon MOSFET in which: a gate electrode is provided in a trench formed in a main surface of a substrate and a field insulating film is formed on the main surface of the substrate and a corner portion formed by a side portion of the trench and the main surface of the substrate.